Method for starting a combustion engine in a hybrid driveline

ABSTRACT

A method is provided to start a combustion engine in a hybrid powertrain, comprising a gearbox with input shaft and output shaft; which combustion engine is connected to the input shaft; a first planetary gear connected to the input shaft; a second planetary gear connected to the first planetary gear; first and second electrical machines, respectively connected to the first and second planetary gears; at least one gear pair, connected with the first planetary gear and the output shaft; and at least one gear pair, connected with the second planetary gear and the output shaft. The method comprises connecting the rotatable components of the second planetary gear with each other by connecting, via a second coupling device, a second sun wheel arranged in the second planetary gear and a second planetary wheel carrier with each other, and activating the first and second electrical machines to start the combustion engine.

CROSS-REFERENCE TO RELATED REFRENCE(S)

This application is a national stage application (filed under 35 §U.S.C. 371) of PCT/SE15/050310, filed Mar. 17, 2015 of the same title,which, in turn claims priority to Swedish Application No. 1450311-4,filed Mar. 20, 2014 of the same title; the contents of each of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method, vehicle, and computer programproduct for starting a combustion engine in a hybrid powertrain.

BACKGROUND OF THE INVENTION

Hybrid vehicles may be driven by a primary engine, which may be acombustion engine, and a secondary engine, which may be an electricalmachine. The electrical machine is equipped with at least one energystorage device, such as an electro-chemical energy storage device, forstorage of electric power and control equipment to control the flow ofelectric power between the energy storage device and the electricalmachine. The electrical machine may thus alternately operate as a motorand as a generator, depending on the vehicle's operating mode. When thevehicle is braked, the electrical machine generates electric power,which is stored in the energy storage device. This is usually referredto as regenerative braking, which entails that the vehicle isdecelerated with the help of the electrical machine and the combustionengine. The stored electric power is used later for operation of thevehicle.

A gearbox in a hybrid vehicle may comprise a planetary gear. Theplanetary gearbox usually comprises three components, which arerotatably arranged in relation to each other, namely a sun wheel, aplanetary wheel carrier and an internal ring gear. With knowledge aboutthe number of cogs in the sun wheel and the internal ring gear, themutual speeds of the three components may be determined duringoperation. One of the components of the planetary gear may be connectedwith an output shaft in a combustion engine. This component of theplanetary gear thus rotates with a rotational speed corresponding to therotational speed of the output shaft in the combustion engine. A secondcomponent in the planetary gear may be connected with an input shaft toa transmission device. This component of the planetary gear thus rotateswith the same rotational speed as the input shaft to the transmissiondevice. A third component in the planetary gear is used to achievehybrid operation, connected with a rotor in an electrical machine. Thiscomponent in the planetary gear thus rotates with the same rotationalspeed as the rotor of the electrical machine, if they are directlyconnected with each other. Alternatively, the electrical machine may beconnected with the third component of the planetary gear via atransmission that has a gearing. In this case, the electrical machineand the third component in the planetary gear may rotate with differentrotational speeds. The engine speed and/or the torque of the electricalmachine may be controlled steplessly. During operating times when theinput shaft to the transmission device must be provided with a desiredrotational speed and/or torque, a control device having knowledge aboutthe engine speed of the combustion engine calculates the rotationalspeed with which the third component must be operated, in order for theinput shaft to the gearbox to obtain the desired rotational speed. Acontrol device activates the electrical machine, so that it provides thethird component with the calculated engine speed and thus the inputshaft to the transmission device with the desired rotational speed.

By connecting the combustion engine's output shaft, the electricalmachine's rotor and the transmission device's input shaft with aplanetary gear, the conventional clutch mechanism may be avoided. Atacceleration of the vehicle, an increased torque must be delivered fromthe combustion engine and the electrical machine to the transmissiondevice, and further to the vehicle's driving wheels. Since both thecombustion engine and the electrical machine are connected with theplanetary gear, the largest possible torque delivered by the combustionengine and the electrical machine will be limited by one of these driveunits; i.e. the one whose maximum torque is lower than the second driveunit's maximum torque, having regard to the gearing between them. Incase the electrical machine's highest torque is lower than thecombustion engine's highest torque, having regard to the gearing betweenthem, the electrical machine will not be able to generate a sufficientlylarge reaction torque to the planetary gear, entailing that thecombustion engine may not transfer its highest torque to thetransmission device and further to the vehicle's driving wheels. Thus,the highest torque that may be transferred to the transmission device islimited by the electrical machine's strength. This is also apparent fromthe so-called planet equation.

Using a conventional clutch, which disconnects the gearbox's input shaftfrom the combustion engine during shifting processes in the gearbox,entails disadvantages, such as heating of the clutch's discs, resultingin wear of the clutch discs and an increased fuel consumption. Aconventional clutch mechanism is also relatively heavy and costly. Italso occupies a relatively large space in the vehicle.

In a vehicle, the space available for the drive arrangement is oftenlimited. If the drive arrangement comprises several components, such asa combustion engine, an electrical machine, a gearbox and a planetarygear, the construction must be compact. If there are additionalcomponents, such as a regenerative braking device, the requirements thatthe component parts must have a compact construction are even morestringent. At the same time, the component parts in the drivearrangement must be designed with dimensions that are able to absorb therequired forces and torque.

For some types of vehicles, especially heavy goods vehicles and buses, alarge number of gear steps is required. Thus, the number of componentparts in the gearbox increases, which must also be dimensioned to beable to absorb large forces and torque arising in such heavy goodsvehicles. This results in an increase of the size and weight of thegearbox.

There are also requirements for high reliability and high dependabilityof the components comprised in the drive device. In case the gearboxcomprises multi-plate clutches, a wear arises, which impacts thereliability and life of the gearbox.

At regenerative braking, kinetic energy is converted into electricpower, which is stored in an energy storage device, such asaccumulators. One factor impacting on the life of the energy storagedevice is the number of cycles in which the energy storage deviceprovides and extracts power to and from the electric machines. The morecycles, the shorter the life of the energy storage device.

Under some operating conditions, it is desirable to shut off thecombustion engine, with the objective of saving fuel and to avoidcooling down of the combustion engine's exhaust treatment system. When atorque injection is required in the hybrid powertrain, or when theenergy storage device must be charged, the combustion engine must bestarted quickly and efficiently.

The document EP-B1-1126987 shows a gearbox with double planetary gears.Each sun wheel of the planetary gear is connected to an electricalmachine, and the internal wheels of the planetary gears are connectedwith each other. The planetary wheel carrier in each planetary gear isconnected to a number of gear pairs, so that an infinite number of gearsteps is obtained. Another document, EP-B1-1280677, also shows how theplanetary gears may be bridged with a gear step arranged on thecombustion engine's output shaft.

The document US-A1-20050227803 shows a vehicle transmission with twoelectrical machines, connected to the respective sun wheels in twoplanetary gears. The planetary gears have a common planetary wheelcarrier, which is connected to the transmission's input shaft.

The document WO2008/046185-A1 shows a hybrid transmission with twoplanetary gears, wherein one electrical machine is connected to one ofthe planetary gears and a double clutch interacts with the secondplanetary gear. Both planetary gears also interact with each other via acogwheel transmission.

SUMMARY OF THE INVENTION

Despite prior art solutions in the field, there is a need to furtherdevelop a hybrid powertrain to achieve the start of the combustionengine.

The objective of the present invention is thus to achieve start of acombustion engine in a hybrid powertrain.

Another objective of the invention is to provide a novel andadvantageous computer program to start a combustion engine.

With the method according to the invention an efficient and reliablestart of the combustion engine is obtained, when the output shaft fromthe gearbox is at a standstill. Such an operating mode may occur whenthe hybrid powertrain is arranged in a vehicle and the vehicle is at astandstill. The combustion engine may be shut off with the objective ofsaving fuel, or to avoid cooling down of the combustion engine's exhaustafter treatment system. If a torque injection is required in the hybridpowertrain line when the vehicle is moved off or when the energy storagesystem must be charged, the combustion engine may be started quickly andefficiently by connecting, according to a first embodiment, the secondplanetary gear's rotatable components with each other, preventing thefirst and the fifth gear pair from rotating, closing the couplingmechanism and activating the first and the second electrical machines,so that the combustion engine starts.

According to a second embodiment of the method, the first and the fifthgear pairs are allowed to rotate freely and the coupling mechanism isallowed to open. The second gear pair is also allowed to rotate freely.The output shaft is prevented from rotating with a brake device for thevehicle's 1 driving wheels, so that the vehicle comes to a standstill.Subsequently, the combustion engine is started by activating the firstand the second electrical machines.

According to a third embodiment of the method, the rotatable componentsof the first and the second planetary gears are connected with eachother. The first, second and fifth gear pairs rotate freely, thecoupling mechanism is open and the brake device for the vehicle'sdriving wheels is released. Subsequently, the combustion engine isstarted by activating the first and the second electrical machines.

The operating mode at the different embodiments above may arise when thevehicle is temporarily parked, and the combustion engine must be startedbecause a torque injection is required to move the vehicle off, or inorder to charge the energy storage system. Similar operating modes mayalso arise when the vehicle has stopped at a traffic light or in atraffic jam.

At an upstart of the combustion engine the systems required in thecombustion engine are activated, such as ignition, fuel pump and airdamper, in order to be able to achieve a fuel combustion process in thecombustion engine.

The electrical machines, which are connected to the planetary gears, maygenerate power or add torque depending on the desired operating mode.The electrical machines may also, at certain operating times, supplyeach other with power.

By connecting a first planetary wheel carrier in the first planetarygear, connected with a second sun wheel in the second planetary gear, afirst sun wheel in the first planetary gear, connected with the firstmain shaft, and a second planetary wheel carrier in the second planetarygear connected with the second main shaft, a transmission that shiftsgears without torque interruption may be obtained.

Suitably, a first planetary wheel carrier in the first planetary gear isdirectly connected with the combustion engine via the input shaft.Alternatively, the first planetary wheel carrier is connected with thecombustion engine via a coupling device. The second planetary wheelcarrier in the second planetary gear is suitably directly connected withthe second main shaft, and therefore with the transmission device. Thus,the hybrid powertrain may transfer a large torque in all operatingmodes, without being dependent on electric power from an energy storagedevice.

According to one embodiment, the first main shaft is connected with asun wheel, arranged in the first planetary gear. Alternatively, thefirst main shaft is connected with an internal ring gear arranged in thefirst planetary gear.

According to one embodiment, the second planetary gear is connected tothe first planetary gear by way of connecting the first planetary wheelcarrier with a second sun wheel, arranged in the second planetary gear.Alternatively, both the planetary gears are connected to each other byway of the first planetary wheel carrier being connected with a secondinternal ring gear, arranged in the second planetary gear.

The gearbox may be equipped with a number of gear pairs, comprisingcogwheels that may be mechanically locked with and released from acountershaft. Thus, a number of fixed gear steps is obtained, which maybe shifted without torque interruption. The cogwheels that may be lockedon the countershaft also result in a compact construction with highreliability and high dependability. Alternatively, pinion gears in thegear pairs may be arranged to be lockable and disconnectable on thefirst and/or second main shaft.

Each of the gear pairs has a gearing, which is adapted to the vehicle'sdesired driving characteristics. The gear pair with the highest gearing,in relation to the other gear pairs, is suitably connected when thelowest gear is engaged.

With the gearbox according to the invention conventional slip clutchesbetween the combustion engine and the gearbox may be avoided.

A locking mechanism is arranged to fixedly connect the combustionengine's output shaft with the gearbox housing. Thus, the firstplanetary wheel carrier will also be locked to the gearbox housing. Bylocking the combustion engine's output shaft with the locking mechanismand the first planetary wheel carrier with the gearbox's housing, thegearbox, and thus the vehicle, becomes adapted for electric operation bythe electrical machines. The electrical machines thus emit a torque tothe output shaft of the gearbox.

A first and second coupling device is arranged between the planetarywheel carrier and the sun wheel of the respective planetary gears. Thetask of the coupling devices is to lock the respective planetary wheelcarriers with the sun wheel. When the planetary wheel carrier and thesun wheel are connected with each other, the power from the combustionengine will pass through the planetary wheel carrier, the couplingdevice, the sun wheel and further along to the gearbox, which entailsthat the planetary wheels do not absorb any torque. This entails thatthe dimension of the planetary wheels may be adapted only to theelectrical machine's torque instead of the combustion engine's torque,which in turn means the planetary wheels may be designed with smallerdimensions. Thus, a drive arrangement according to the invention isobtained, which has a compact construction, a low weight and a lowmanufacturing cost.

The coupling devices and the locking mechanisms preferably comprise anannular sleeve, which is shifted axially between a connected and adisconnected state. The sleeve encloses, substantially concentrically,the gearbox's rotating components and is moved between the connected anddisconnected state with a power element. Thus, a compact construction isobtained, with a low weight and a low manufacturing cost.

In order to connect, with the first and the second coupling device,respectively, the sun wheel and the planetary wheel carrier of therespective planetary gear, the combustion engine and/or the firstelectrical machine and/or the second electrical machine is controlled insuch a way that a synchronous rotational speed is achieved between thesun wheel and the planetary wheel carrier. When a synchronous rotationalspeed has been achieved, the coupling device is shifted, so that the sunwheel and the planetary wheel carrier become mechanically connected witheach other.

In order to disconnect the respective planetary gear's planetary wheelcarrier and sun wheel from each other, the first and/or secondelectrical machine is controlled, so that torque balance is achieved inthe planetary gear. When torque balance has been achieved, the couplingdevice is shifted, so that the sun wheel and the planetary wheel carrierare no longer mechanically connected with to each other.

Torque balance relates to a state where a torque acts on an internalring gear arranged in the planetary gear, representing the product ofthe torque acting on the planetary wheel carrier of the planetary gearand the gear ratio of the planetary gear, while simultaneously a torqueacts on the planetary gear's sun wheel, representing the product of thetorque acting on the planetary wheel carrier and (1- the planetarygear's gear ratio). In the event two of the planetary gear's componentparts, i.e. the sun wheel, the internal ring gear or planetary wheelcarriers, are connected with a coupling device, this coupling devicedoes not transfer any torque between the planetary gear's parts whentorque balance prevails. Accordingly, the coupling device may easily beshifted and the planetary gear's component parts be disconnected.

BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description, as an example, of preferred embodiments of theinvention with reference to the enclosed drawings, on which:

FIG. 1 schematically shows a vehicle in with a combustion engine a sideview, arranged to be started according to the method, according to thepresent invention,

FIG. 2 shows a schematic side view of a hybrid powertrain with acombustion engine, which is arranged to be started according to themethod, according to the present invention,

FIG. 3 shows a schematic view of a hybrid drive line with a combustionengine, which is arranged to be started according to the method,according to the present invention, and

FIG. 4, FIG. 5, and FIG. 6 show flow charts of embodiments of the methodto start a combustion engine in a hybrid powertrain according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a schematic side view of a vehicle 1, comprising a gearbox2 and a combustion engine 4, which are comprised in a hybrid powertrain3. The combustion engine 4 is connected to the gearbox 2, and thegearbox 2 is further connected to the driving wheels 6 of the vehicle 1via a propeller shaft 9. The driving wheels 6 are equipped with brakedevices 7 to brake the vehicle 1.

FIG. 2 shows a schematic side view of a hybrid powertrain 3 with agearbox 2, comprising an input shaft 8, a first and a second planetarygear 10 and 12, respectively, a first and a second electrical machine 14and 16, respectively, a countershaft 18 and an output shaft 20. Thehybrid powertrain comprises a combustion engine 4, connected to thegearbox 2. The combustion engine 4 is connected with the gearbox 2 viathe input shaft 8 of the gearbox. The combustion engine has an outputshaft 97. The output shaft 97 of the combustion engine 4 is connected tothe input shaft of the gearbox 2. The first planetary gear 10 has afirst internal ring gear 22, to which a first rotor 24 in the firstelectrical machine 14 is connected. The first planetary gear 10 also hasa first sun wheel 26 and a first planetary wheel carrier 50. The firstplanetary wheel carrier 50 is connected with the combustion engine 4 viathe input shaft 8 of the gearbox. The second planetary gear 12 has asecond internal ring gear 28, to which a second rotor 30 of the secondelectrical machine 16 is connected. The second planetary gear 12 has asecond sun wheel 32 and a second planetary wheel carrier 51. The firstand the second sun wheels 26 and 32, respectively, are coaxiallyarranged, which, according to the embodiment displayed, entails that afirst main shaft 34 arranged on the first sun wheel 26 extends inside asecond main shaft 36, which is equipped with a central boring 38,arranged on the second planetary wheel carrier 51. It is also possibleto arrange the first and second sun wheels 26 and 32, respectively, andalso the first main shaft 34 and the second main shaft 36, in parallelwith and next to each other. In this case, the countershaft 18 issuitably arranged between the first main shaft 34 and the second mainshaft 36, and the torque may be extracted directly from the countershaft18. The countershaft 18 thus constitutes, in this case, the output shaft20.

The combustion engine 4 is connected with the first planetary wheelcarrier 50, and the first planetary wheel carrier 50 is connected withthe second sun wheel 32.

The first electrical machine 14 is equipped with a first stator 40,which is connected to the vehicle 1, via a gear housing 42 surroundingthe gearbox 2. The second electrical machine 16 is equipped with asecond stator 44, which is connected to the vehicle 1, via a gearhousing 42 surrounding the gearbox 2. The first and the secondelectrical machine 16 are connected to an energy storage device 46, suchas a battery, which, depending on the vehicle's 1 operating mode,operates the electrical machines 14 and 16, respectively. At otheroperating modes, the electrical machines 14 and 16, respectively, maywork as generators, wherein power is supplied to the energy storagedevice 46. An electronic control device 48 is connected to the energystorage device 46 and controls the supply of power to the electricalmachines 14 and 16, respectively. Preferably the energy storage device46 is connected to the electrical machines 14 and 16, respectively, viaa switch 49, which is connected to the control device 48. In someoperating modes, the electrical machines 14 and 16, respectively, mayalso operate each other. Electric power is then led from one of theelectrical machines 14, 16 to the second electrical machine 14, 16 viathe switch 49, connected to the electrical machines 14, 16. Thus, it ispossible to achieve a power balance between the electrical machines 14,16. Another computer 53 may also be connected to the control device 48and the gearbox 2.

The first planetary gear 10 is equipped with a first planetary wheelcarrier 50, on which a first set of planetary wheels 52 is mounted. Thesecond planetary gear 12 is equipped with a second planetary wheelcarrier 51, on which a second set of planetary wheels 54 is mounted. Thefirst set of planetary wheels 52 interacts with the first internal ringgear 22 and the first sun wheel 26. The second set of planetary wheels54 interacts with the second internal ring gear 28 and the second sunwheel 32. The input shaft 8 of the gearbox 2 is connected with the firstplanetary wheel carrier 50.

A first coupling device 56 is arranged between the first sun wheel 26and the first planetary wheel carrier 50. By arranging the firstcoupling device 56 in such a way that the first sun wheel 26 and thefirst planetary wheel carrier 50 are connected with each other, and maytherefore not rotate in relation to each other, the first planetarywheel carrier 50 and the first sun wheel 26 will rotate with equalrotational speeds.

A second coupling device 58 is arranged between the second sun wheel 32and the second planetary wheel carrier 51. By arranging the secondcoupling device 58 in such a way that the second sun wheel 32 and thesecond planetary wheel carrier 51 are connected with each other, and maytherefore not rotate in relation to each other, the second planetarywheel carrier 51 and the first sun wheel 32 will rotate with equalrotational speeds.

Preferably, the first and second coupling devices 56, 58 comprise afirst and a second splines-equipped coupling sleeve 55 and 57,respectively, which is axially shiftable on a splines-equipped sectionon the first and second, respectively, planetary wheel carrier 50 and51, and on a splines-equipped section on the respective sun wheels 26and 32. By shifting the respective coupling sleeve 55, 57 so that thesplines-equipped sections are connected via the respective couplingsleeves 55, 57, the first planetary wheel carrier 50 and the first sunwheel 26, as well as the second planetary wheel carrier 51 and thesecond sun wheel 32, respectively, become mutually interlocked with eachother and may not rotate in relation to each other.

The first and second coupling device 56, 58 according to the embodimentdisplayed in FIG. 2 are arranged between the first sun wheel 26 and thefirst planetary wheel carrier 50, and between the second sun wheel 28and the second planetary wheel carrier 51, respectively. However, it ispossible to arrange an additional or alternative coupling device (notdisplayed) between the first internal ring gear 22 and the firstplanetary wheel carrier 50, and also to arrange an additional oralternative coupling device (not displayed) between the second internalring gear 28 and the second planetary wheel carrier 51.

The first planetary wheel carrier 50 of the first planetary gear 10 inthis embodiment is fixedly connected with the second sun wheel 32 of thesecond planetary gear 12. Alternatively, the first planetary wheelcarrier 50 is fixedly connected with the second internal ring gear 28 ofthe second planetary gear 12.

In this embodiment, a third coupling device 59 is arranged between thefirst ring gear 22 and the gear house 42. By actuating the thirdcoupling device 59, so that the first ring gear 22 and the gear house 42are connected with each other and accordingly may not rotate in relationto each other, a down-shift of torque will occur, that is to say anup-shift of the rotational speed from the planetary wheel carrier 50 tothe first sun wheel 26 will occur.

In this embodiment, a fourth coupling device 61 is arranged between thesecond internal ring gear 28 and the gear house 42. By actuating thefourth coupling device 61, so that the second ring gear 28 and the gearhouse 42 are connected with each other, and accordingly may not rotatein relation to each other, a down-shift of torque will occur, that is tosay an up-shift of the rotational speed will occur from the planetarywheel carrier 50 to the second sun wheel 32.

Preferably the third and fourth coupling device 59, 61 comprises a thirdand fourth splines equipped coupling sleeve 65 and 67, respectively,which are axially shiftable on the respective splines-equipped sectionsof the first and second ring gears 22 and 28, as well as on asplines-equipped section of the gear house 42. By shifting therespective coupling sleeves 65, 67 in such a way that thesplines-equipped sections are connected via the respective couplingsleeves 65, 67, the first ring gear 22 and the gear house 42, and thesecond ring gear 28 and the gear house 42, respectively, are interlockedand may not rotate in relation to each other.

A transmission device 19, which comprises a first gear pair 60, arrangedbetween the first planetary gear 10 and the output shaft 20 is connectedto the first and the second main shaft 34, 36. The first gear pair 60comprises a first pinion gear 62 and a first cogwheel 64, which are inengagement with each other. A second gear pair 66 is arranged betweenthe second planetary gear 12 and the output shaft 20. The second gearpair 66 comprises a second pinion gear 68 and a second cogwheel 70,which are in engagement with each other. A third gear pair 72 isarranged between the first planetary gear 10 and the output shaft 20.The third gear pair 72 comprises a third pinion gear 74 and a thirdcogwheel 76, which are in engagement with each other. A fourth gear pair78 is arranged between the second planetary gear 12 and the output shaft20. The fourth gear pair 78 comprises a fourth pinion gear 80 and afourth cogwheel 82, which are in engagement with each other.

On the first main shaft 34, the first and the third pinion gears 62 and74, respectively, are arranged. The first and the third pinion gears 62and 74, respectively, are fixedly connected with the first main shaft34, so that they may not rotate in relation to the first main shaft 34.On the second main shaft 36, the second and the fourth pinion gears 68and 80, respectively, are arranged. The second and the fourth piniongears 68 and 80, respectively, are fixedly connected with the secondmain shaft 36, so that they may not rotate in relation to the secondmain shaft 36.

The countershaft 18 extends substantially in parallel with the first andthe second main shaft 34 and 36, respectively. On the countershaft 18,the first, second, third and fourth cogwheels 64, 70, 76 and 82,respectively, are mounted. The first pinion gear 62 engages with thefirst cogwheel 64, the second pinion gear 68 engages with the secondcogwheel 70, the third pinion gear 74 engages with the third cogwheel 76and the fourth pinion gear 80 engages with the fourth cogwheel 82.

The first, second, third and fourth cogwheels 64, 70, 76 and 82,respectively, may be individually locked with and released from thecountershaft 18 with the assistance of the first, second, third andfourth coupling elements 84, 86, 88 and 90, respectively. The couplingelements 84, 86, 88 and 90, respectively, preferably consist ofsplines-equipped sections on the cogwheels 64, 70, 76 and 82,respectively, and on the countershaft 18, which interact with fifth andsixth coupling sleeves 83, 85 which engage mechanically with thesplines-equipped sections of the respective first to fourth cogwheel 64,70, 76 and 82 and of the countershaft 18. The first and third couplingelements 84, 88 are preferably equipped with a common coupling sleeve83, and the second and fourth coupling elements 86, 90 are preferablyequipped with a common coupling sleeve 85. In the released state, arelative rotation may occur between the cogwheels 64, 70, 76 and 82 andof the countershaft 18. The coupling elements 84, 86, 88 and 90,respectively, which may also consist of friction clutches. On thecountershaft 18 a fifth cogwheel 92 is also arranged, which engages witha sixth cogwheel 94, which is arranged on the output shaft 20 of thegearbox 2.

The countershaft 18 is arranged between the respective first and secondplanetary gears 10, 12 and the output shaft 20, so that the countershaft18 is connected with the output shaft 20 via a fifth gear pair 21, whichcomprises the fifth and the sixth cogwheel 92, 94. The fifth cogwheel 92is arranged so it may be connected with and disconnected from thecountershaft 18 with a fifth coupling element 93.

By disconnecting the fifth cogwheel 92, which is arranged to bedisconnectable from the countershaft 18, it is possible to transfertorque from the second planetary gear 12 to the countershaft 18 via thesecond gear pair 66, and to further transfer torque from thecountershaft 18 to the output shaft 20 via the first gear pair 60. Thus,a number of gear steps is obtained, wherein torque from one of theplanetary gears 10, 12 may be transferred to the countershaft 18, andfurther along from the countershaft 18 to the main shaft 34, 36connected with the second planetary gear 10, 12, finally to transfertorque to the output shaft 20 of the gearbox 2. This presumes, however,that a coupling mechanism 96 arranged between the first main shaft 34and the output shaft 20 is connected, which is described in more detailbelow.

The fifth cogwheel 92 may be locked to and released from thecountershaft 18 with the assistance of a fifth coupling element 93. Thecoupling element 93 preferably consists of splines-equipped sectionsadapted on the fifth cogwheel 92 and the countershaft 18, which sectionsinteract with a ninth coupling sleeve 87, which engages mechanicallywith the splines-equipped sections of the fifth cogwheel 92 and thecountershaft 18. In the released state, a relative rotation may occurbetween the fifth cogwheel 92 and the countershaft 18. The fifthcoupling element 93 may also consist of friction clutches.

At a number of gearing situations, wherein the ring gears of theplanetary gears 10, 12 are locked with the gear house 42 with theassistance of the third and fourth coupling devices 59, 61, torque willbe downshifted after the first planetary gear 10 and up-shifted afterthe second planetary gear 12. When the torque transfer over the firstmain shaft 34 via the countershaft 18 decreases after the firstplanetary gear 10, shafts, pinion gears and cogwheels connected theretomay be designed to be smaller, which makes the gearbox 2 more compact. Alarge number of gear steps may also be obtained without any need toarrange a number of additional gear pairs in the gearbox. Accordingly,the weight and cost of the gearbox 2 are also reduced. The fifth andsixth cogwheels 92 and 94 will function like a fifth gear pair 21,transferring torque to the output shaft 20 of the gearbox 2.

Torque transfer from the input shaft 8 of the gearbox 2 to the outputshaft 20 of the gearbox 2 may occur via the first or the secondplanetary gear 10 and 12, respectively, and the countershaft 18. Thetorque transfer may also occur directly via the first planetary gear 10,whose first sun wheel 26 is connected, via the first main shaft 34, tothe output shaft 20 of the gearbox 2 via a coupling mechanism 96. Thecoupling mechanism 96 preferably comprises a splines-equipped seventhcoupling sleeve 100, which is axially shiftable on the first main shaft34 and on the splines-equipped sections of the output shaft 20. Byshifting the seventh coupling sleeve 100, so that the splines-equippedsections are connected via the seventh coupling sleeve 100, the firstmain shaft 34 becomes locked with the output shaft 20, which, whenrotating, will therefore have the same rotational speed. Bydisconnecting the fifth cogwheel 92 of the fifth gear pair 21 from thecountershaft 18, torque from the second planetary gear 12 may betransferred to the countershaft 18, and further along from thecountershaft 18 to the first main shaft 34, connected with the firstplanetary gear 10, in order finally to transfer torque via the couplingmechanism 96 to the output shaft 20 of the gearbox 2.

In some operating modes the gearbox 2 may operate so that one of the sunwheels 26 and 32, respectively, are locked with the first and the secondplanetary wheel carrier 50 and 51, respectively, with the help of thefirst and the second coupling device 56 and 58, respectively. The firstand the second main shaft 34 and 36, respectively, then obtain the samerotational speed as the input shaft 8 of the gearbox 2, depending onwhich sun wheel 26 and 32, respectively, is locked with the respectiveplanetary wheel carriers 50 and 51. One or both of the electricalmachines 14 and 16, respectively, may operate as a generator to generateelectric power to the energy storage device 46. Alternatively, theelectrical machine 14 and 16, respectively, may provide a torqueinjection, in order to thus increase the torque in the output shaft 20.At some operating times, the electrical machines 14 and 16,respectively, will supply each other with electric power, independentlyof the energy storage device 46.

In some operating modes the gearbox 2 may operate in such a way that oneof the rotors 24 and 30, respectively, of the electrical machines 14 and16, respectively, is locked with the gear house 42 via the respectivering gears 22 and 28, while the second electrical machine 14 and 16,respectively, operate as a generator to generate electric power to theenergy storage device 46, which will be explained in more detail below.The electrical machine 14 and 16, respectively, whose respective rotor24 and 30, is locked with the gear house 42, absorbs a reaction torquefrom the ring gear 22 and 28, respectively, so that torque balanceprevails before the locking is carried out with the help of the thirdand fourth coupling devices 59 and 61, respectively. Instead ofoperating as a generator, the electrical machines 14 and 16,respectively, may provide a torque injection, in order to thus increasethe torque in the output shaft 20. Torque balance comprises asubstantially zero torque state on the one hand, and a counteractingtorque on the other, in order for the coupling devices 59, 61 to be putinto a state, wherein they do not transfer torque between the ring gears22, 28 and the gear house 42.

It is also possible that the total reaction torque of both the first andthe second electrical machine 14 and 16, respectively, generate power tothe energy storage device 46. At engine braking the driver releases theaccelerator pedal (not displayed) of the vehicle 1. The output shaft 20of the gearbox 2 then operates one or both electrical machines 14 and16, respectively, while the combustion engine 4 and the electricalmachines 14 and 16, respectively, engine brake. The electrical machines14 and 16, respectively, in this case generate electric power, which isstored in the energy storage device 46 in the vehicle 1. This operatingstate is referred to as regenerative braking. In order to facilitatemore powerful braking effect the output shaft 97 of the combustionengine's 4 may be locked and thus be prevented from rotating. Thus, onlyone of or both the electrical machines 14 and 16, respectively, willfunction as brakes and 16 generate electric power, which is stored inthe energy storage device 46. The locking of the output shaft 97 of thecombustion engine 4 may also be carried out when the vehicle mustaccelerate by only one or both the electrical machines 14 and 16,respectively. If the torque of one or both of the respective electricalmachines 14 and 16 overcomes the torque off the combustion engine 4, andhaving regard to the gearing between them, the combustion engine 4 willnot be able to resist the large torque which the respective electricalmachines 14 and 16 generate, so that it becomes necessary to lock theoutput shaft 97 of the combustion engine's 4. The locking of the outputshaft 97 of the combustion engine 4 is preferably carried out with alocking device 102, which is arranged between the first planetary wheelcarrier 50 and the gear hosing 42. By locking the first planetary wheelcarrier 50 and the gear housing 42, the output shaft 97 of thecombustion engine 4 will also be locked, since the output shaft 97 ofthe combustion engines 4 is connected with the first planetary wheelcarrier 50 via the input shaft 8 of the gearbox. The locking device 102preferably comprises a splines-equipped eighth coupling sleeve 104,which is axially shiftable on a splines-equipped section of the firstplanetary wheel carrier 50, and on a splines-equipped section of thegear housing. By shifting the eight coupling sleeve 104 so that thesplines-equipped sections are connected via the coupling sleeve 104, thefirst planetary wheel carrier 50, and therefore the output shaft 97 ofthe combustion engine 4 is prevented from rotating.

The control device 48 is connected to the electrical machines 14 and 16,respectively, to control the respective electrical machines 14 and 16,so that they, during certain operating times, use stored electric powerto supply driving power to the output shaft 20 of the gearbox 2, andduring other operating times use the kinetic energy of the output shaft20 of the gearbox 2 to extract and store electric power. The controldevice 48 thus detects the rotational speed and/or the torque of theoutput shaft 97 of the combustion engine 4 via sensors 98 arranged atthe electrical machines 14 and 16, respectively, and in the output shaft20 of the gearbox 2, in order thus to gather information and to controlthe electrical machines 14 and 16, respectively, to operate as electricmotors or generators. The control device 48 may be a computer withsoftware suitable for this purpose. The control device 48 also controlsthe flow of power between the energy storage device 46 and therespective stators 40 and 44 of the electrical machines 14 and 16,respectively. At times when the electrical machines 14 and 16,respectively, operate as engines, stored electric power is supplied fromthe energy storage device 46 to the respective stators 40 and 44. Attimes when the electrical machines 14 and 16 operate as generatorselectric power is supplied from the respective stators 40 and 44 to theenergy storage device 46. However, as stated above, the electricalmachines 14 and 16, respectively, may, during certain operating times,supply each other with electric power, independently of the energystorage device 46.

The first, second, third and fourth coupling devices 56, 58, 59 and 61,respectively, the first, second, third, fourth and fifth couplingelements 84, 86, 88, 90 and 93, respectively, the coupling mechanism 96between the first main shaft 34 and the output shaft 20, and the lockingdevice 102 between the first planetary wheel carrier 50 and the gearhousing 42, are connected to the control device 48 via their respectivecoupling sleeves. These components are preferably activated anddeactivated by electric signals from the control device 48. The couplingsleeves are preferably shifted by non-displayed power elements, such ashydraulically or pneumatically operated cylinders. It is also possibleto shift the coupling sleeves with electrically powered power elements.

The example embodiment in FIG. 2 shows four pinion gears 62, 68, 74 and80, respectively, and four cogwheels 64, 70, 76 and 82, respectively,and two respective planetary gears 10 and 12 with associated electricalmachines 14 and 16, respectively. However, it is possible to adapt thegearbox 2 with more or fewer pinion gears and cogwheels, and with moreplanetary gears with associated electrical machines.

Below, an up-shift from the first to the highest gear will be described,wherein the gearbox 2 is arranged in a vehicle 1. The input shaft 8 ofthe gearbox 2 is connected with the output shaft 97 of the combustionengine 4 of the vehicle 1. The output shaft 20 of the gearbox 2 isconnected to a driving shaft 99 in the vehicle 1. At idling of thecombustion engine 4 and when the vehicle 1 is at a standstill, the inputshaft 8 of the gearbox 2 rotates at the same time as the output shaft 20of the gearbox 2 is at a standstill. The locking device 102 isdeactivated, so that the output shaft 97 of the combustion engine 4 mayrotate freely. Since the input shaft 8 of the gearbox 2 rotates, thefirst planetary wheel carrier 50 will also rotate, which entails thatthe first set of planetary wheels 52 will rotate. Since the firstplanetary wheel carrier 50 is connected to the second sun wheel 32, thesecond sun wheel 32, and thus also the second set of planetary wheels54, will rotate. By not supplying power to, or extracting power from,the first and the second electrical machines 14 and 16, respectively,the first and the second internal rings 22 and 28, respectively, whichare connected with the respective first and second rotor 24 and 30 ofthe electrical machines 14 and 16, respectively, will rotate freely, sothat no torque is absorbed by the respective internal rings 22 and 28.The first, second, third and fourth coupling devices 56, 58, 59 and 61,respectively, are disconnected and thus not actuated. Thus, no torquewill be transferred from the combustion engine 4 to the respective sunwheels 26 and 32 of the planetary gears 10 and 12. The couplingmechanism 96 between the first main shaft 34 and the output shaft 20 isdisconnected, so that the first main shaft 34 and the output shaft 20may rotate freely in relation to each other. Since the output shaft 20of the gearbox 2 at this stage is at a standstill, the countershaft 18is also at a standstill. In a first step the fourth cogwheel 82 and thethird cogwheel 76 are connected with the countershaft 18 with theassistance of the fourth and third coupling elements 90 and 88,respectively. The first cogwheel 64 and the second cogwheel 70 aredisconnected from the countershaft 18. Thus, the first cogwheel 64 andthe second cogwheel 70 are allowed to rotate freely in relation to thecountershaft 18. The fifth cogwheel 92 of the fifth gear pair 21 islocked on the countershaft 18 with the assistance of the fifth couplingelement 93.

In order to start the rotation of the output shaft 20 of the gearbox 2,with the objective of driving the vehicle 1, the fourth pinion gear 80and the fourth cogwheel 82 on the countershaft 18 must be brought torotate. This is achieved by making the second planetary wheel carrier 51rotate. When the second planetary wheel carrier rotates, the second mainshaft 36 will also rotate, and thus the fourth pinion gear 80, which isarranged on the second main shaft 36, also rotates. The second planetarywheel carrier 51 is made to rotate by controlling the second internalring gear 28 with the second electrical machine 16. By activating thesecond electrical machine 16 and controlling the combustion engine 4 toa suitable engine speed, the vehicle 1 begins to move as the second mainshaft 36 begins to rotate. When the second planetary wheel carrier 51and the second sun wheel 32 achieve the same rotational speed, thesecond sun wheel 32 is locked with the second planetary wheel carrier 51with the assistance of the second coupling device 58. As mentionedabove, the second coupling device 58 is preferably adapted in such a waythat the second sun wheel 32 and the second planetary wheel carrier 51engage mechanically with each other. Alternatively, the second couplingdevice 58 may be adapted as a slip brake or a multi-plate clutch whichconnects, in a smooth way, the second sun wheel 32 with the secondplanetary wheel carrier 51. When the second sun wheel 32 is connectedwith the second planetary wheel carrier 51, the second planetary wheelcarrier 51 will rotate with the same rotational speed as the outputshaft 97 of the combustion engine 4. Thus, the torque generated by thecombustion engine 4 is transferred to the output shaft 20 of the gearbox2 via the fourth pinion gear 80, the fourth cogwheel 82 on thecountershaft 18, the fifth cogwheel 92 on the countershaft 18, and thesixth cogwheel 94 on the output shaft 20 of the gearbox 2. The vehicle 1will thus begin to move off and be propelled by the first gear.

Each of the first, second, third and fourth gear pairs 60, 66, 72, 78has a gearing, which is adapted to the vehicle's 1 desired drivingcharacteristics. According to the example embodiment displayed in FIG.2, the fourth gear pair 78 has the highest gearing compared to thefirst, second and third gear pairs 60, 66, 72, which results in thefourth gear pair 78 being connected when the lowest gear is engaged. Thesecond gear pair 66 transfers, as does the fourth gear pair 78, torquebetween the second main shaft 36 and the countershaft 18, and couldinstead be fitted out with the highest gearing, compared with other gearpairs 60, 72, 78, which is why in such an embodiment the second gearpair 66 could be connected when the lowest gear is engaged.

When the countershaft 18 is made to rotate by the fourth cogwheel 82 onthe countershaft 18, the third cogwheel 76 on the countershaft 18 willalso rotate. Thus, the countershaft 18 operates the third cogwheel 76,which in turn operates the third pinion gear 74 on the first main shaft34. When the first main shaft 34 rotates, the first sun wheel 26 willalso rotate, and thus, depending on the rotational speed of the outputshaft 97 of the combustion engine 4 and thus the rotational speed of thefirst planetary wheel carrier 50, it will cause the first internal ringgear 22 and the first rotor 24 of the first electrical machine 14 torotate. It is thus possible to allow the first electrical machine 14 tooperate as a generator to supply power to the energy storage device 46,and/or to supply power to the second electrical machine 16. It is alsopossible for the second electrical machine 16 to be operated as agenerator. Alternatively, the first electrical machine 14 may emit atorque injection, by way of the control device 48 controlling the firstelectrical machine 14 to provide a driving torque.

In order to shift from a first gear to a second gear, the lockingbetween the second sun wheel 32 and the second planetary wheel carrier51 must cease, which is achieved by way of the first and/or the secondelectrical machine 14, 16 being controlled in such a way that torquebalance prevails in the second planetary gear 12. Subsequently, thesecond coupling device 58 is controlled, so that it disconnects thesecond sun wheel 32 and the second planetary wheel carrier 51 from eachother. The second planetary wheel carrier 51 and also the second mainshaft 36 may rotate freely, which entails that the second sun wheel 32,the second planetary wheel carrier 51 and the second main shaft 36 nolonger operate the fourth pinion gear 80, arranged on the second mainshaft 36. This assumes that the second electrical machine 16 does notoperate the second ring gear 28. The second gear is connected, by way ofthe control device 48 controlling the combustion engine 4, so that asynchronous rotational speed arises between the first planetary wheelcarrier 50 and the first sun wheel 26, in order to achieve a lockingbetween the first planetary wheel carrier 50 and the first sun wheel 26.This is achieved by way of controlling the first coupling device 56 insuch a way that the first planetary wheel carrier 50 and the first sunwheel 26 are mechanically connected with each other. Alternatively, thefirst coupling device 56 may be adapted as a slip brake or a multi-plateclutch which connects, in a smooth way, the first sun wheel 26 with thefirst planetary wheel carrier 50. By synchronizing the control of thecombustion engine 4 and the second and first electrical machine 14 and16, respectively, a soft and disruption-free transition from the firstto the second gear may be carried out.

The first main shaft 34 now rotates, operated by the output shaft 97 ofthe combustion engine 4, and the first main shaft 34 now operates thethird pinion gear 74. Thus, the first planetary wheel carrier 50 nowoperates the third pinion gear 74, via the first sun wheel 26 and thefirst main shaft 34. Since the third cogwheel 76 is in engagement withthe third pinion gear 74 and is connected with the countershaft 18, thethird cogwheel 76 will operate the countershaft 18, which in turnoperates the fifth cogwheel 92 on the countershaft 18. The fifthcogwheel 92 in turn operates the output shaft 20 of the gearbox 2 viathe sixth cogwheel 94, which is arranged on the output shaft 20 of thegearbox 2. The vehicle 1 is now driven with the second gear engaged.

When the countershaft 18 is made to rotate by the third cogwheel 76, thefourth cogwheel 82 will also rotate. Thus, the countershaft 18 operatesthe fourth cogwheel 82, which in turn operates the fourth pinion gear 80on the second main shaft 36. When the second main shaft 36 rotates, thesecond planetary wheel carrier 51 will also rotate, and thus, dependingon the rotational speed of the output shaft 97 of the combustion engine4, and thus the rotational speed in the first planetary wheel carrier50, it will cause the second internal ring gear 28 and the second rotor30 of the second electrical machine 16 to rotate. It is thus possible toallow the second electrical machine 16 to operate as a generator tosupply power to the energy storage device 46, and/or to supply power tothe first electrical machine 14. The second electrical machine 16 mayalso emit a torque injection, by way of the control device 48controlling the second electrical machine 16 to provide a propulsiontorque.

In order to shift from the second gear to the third gear, the fourthcogwheel 82 on the countershaft 18 must be disconnected from thecountershaft 18 with the fourth coupling element 90, so that the fourthcogwheel 82 may rotate freely in relation to the countershaft 18.Subsequently, the countershaft 18 is connected with the second cogwheel70 on the countershaft 18 via the second coupling element 86. In orderto achieve a connection of the countershaft 18 and the second cogwheel70 on the countershaft 18, preferably the second electrical machine 16is controlled in such a way that a synchronous rotational speed arisesbetween the countershaft 18 and the second cogwheel 70 on thecountershaft 18. A synchronous rotational speed may be achieved by wayof measuring the rotational speed in the second rotor 30 in the secondelectrical machine 16, and measuring the rotational speed in the outputshaft 20. Thus, the rotational speed in the second main shaft 36 and therotational speed in the countershaft 18 may be determined by way ofgiven gear ratios. The rotational speed of the respective shafts 18, 36is controlled, and when a synchronous rotational speed has arisenbetween the countershaft 18 and the second cogwheel 70, the countershaft18 and the second cogwheel 70 are connected with the assistance of thesecond coupling element 86.

In order to complete the shift from a second gear to the third gear, thelocking between the first sun wheel 26 and the first planetary wheelcarrier 50 must cease, which is achieved by way of the first and/or thesecond electrical machine 14, 16 being controlled in such a way thattorque balance prevails in the first planetary gear 10, following whichthe first coupling device 56 is controlled, in such a way that itdisconnects the first sun wheel 26 and the first planetary wheel carrier50 from each other. Subsequently, the combustion engine 4 is controlledin such a way that a synchronous rotational speed arises between thesecond sun wheel 32 and the second planetary wheel carrier 51, so thatthe second coupling device 58 may be engaged in order thus to connectthe second sun wheel 32 with the second planetary wheel carrier 51, viathe coupling sleeve 57. By synchronizing the control of the combustionengine 2 and the second and first electrical machine 14 and 16,respectively, a soft and disruption-free transition from the second tothe third gear may be carried out.

The third cogwheel 76 is disconnected by controlling the firstelectrical machine 14 in such a way that a substantially zero torquestate arises between the countershaft 18 and the third cogwheel 76. Whena substantially zero torque state arises, the third cogwheel 76 isdisconnected from the countershaft 18 by controlling the third couplingelement 88, so that it releases the third cogwheel 76 from thecountershaft 18. Subsequently, the first electrical machine 14 iscontrolled in such a way that a synchronous rotational speed arisesbetween the countershaft 18 and the first cogwheel 64. When asynchronous rotational speed arises, the first cogwheel 64 is connectedto the countershaft 18 by way of controlling the first coupling element84, so that it connects the first cogwheel 64 on the countershaft 18. Asynchronous rotational speed may be determined, since the rotationalspeed of the first rotor 24 in the first electrical machine 14 ismeasured and the rotational speed of the output shaft 20 is measured,following which the rotational speeds of the shafts 18, 34 arecontrolled in such a way that a synchronous engine speed arises. Thus,the rotational speed of the first main shaft 34 and the rotational speedof the countershaft 18 may be determined by way of given gear ratios.

The second main shaft 36 now rotates with the same rotational speed asthe output shaft 97 of the combustion engine 4, and the second mainshaft 36 now operates the second pinion gear 68 via the second mainshaft 36. Since the second cogwheel 70 is in engagement with the secondpinion gear 68 and is connected with the countershaft 18, the secondcogwheel 70 will operate the countershaft 18, which in turn operates thefifth cogwheel 92 on the countershaft 18. The fifth cogwheel 92 in turnoperates the output shaft 20 of the gearbox 2 via the sixth cogwheel 94,which is arranged on the output shaft 20 of the gearbox 2. The vehicle 1is now driven in a third gear.

When the countershaft 18 is made to rotate by the second cogwheel 70 onthe countershaft 18, the first cogwheel 64 on the countershaft 18 willalso rotate. Thus, the countershaft 18 operates the first cogwheel 64,which in turn operates the first pinion gear 62 on the first main shaft34. When the first main shaft 34 rotates, the first sun wheel 26 willalso rotate, and thus, depending on the rotational speed of the outputshaft 97 of the combustion engine 4, and thus the rotational speed ofthe first planetary wheel carrier 50, it will cause the first internalring gear 22 and the first rotor 24 of the second electrical machine 16to rotate. It is thus possible to allow the first electrical machine 14operate as a generator to supply power to the energy storage device 46,and/or to supply power to the second electrical machine 16.Alternatively, the first electrical machine 14 may emit a torqueinjection, by way of the control device 48 controlling the firstelectrical machine 14 to provide a driving torque.

In order to complete the shift from the third to the fourth gear, thelocking between the second sun wheel 32 and the second planetary wheelcarrier 51 must cease, which is achieved by way of the first and/or thesecond electrical machine 14, 16 being controlled in such a way thattorque balance is created in the second planetary gear 12, followingwhich the second coupling device 58 is controlled in such a way that itdisconnects the second sun wheel 32 and the second planetary wheelcarrier 51 from each other. Subsequently, the first ring gear 22 isdecelerated, and when the first ring gear 22 is at a standstill thethird coupling device 59 is controlled in such a way that the first ringgear 22 is connected and joined with the gear house 42. By synchronizingthe control of the combustion engine 4 and the second and firstelectrical machine 14 and 16, respectively, a soft and disruption-freetransition from a third to a fourth gear may be carried out.

The first main shaft 34 is now operated by the output shaft 97 of thecombustion engine 4, and the first main shaft 34 now operates the firstpinion gear 62. Since the first cogwheel 64 is in engagement with thefirst pinion gear 62 and is connected with the countershaft 18, thefirst cogwheel 64 will operate the countershaft 18, which in turnoperates the fifth cogwheel 92 on the countershaft 18. The fifthcogwheel 92 in turn operates the output shaft 20 of the gearbox 2 viathe sixth cogwheel 94, which is arranged on the output shaft 20 of thegearbox 2. The vehicle 1 is now driven in a fourth gear.

When the countershaft 18 is made to rotate by the first cogwheel 64, thesecond cogwheel 70 on the countershaft 18 will also rotate. Thus, thecountershaft 18 operates the second cogwheel 70, which in turn operatesthe second pinion gear 68 on the second main shaft 36. When the secondmain shaft 36 rotates, the second planetary wheel carrier 51 will alsorotate, and thus, depending on the rotational speed of the output shaft97 of the combustion engine 4 and thus the rotational speed in the firstplanetary wheel carrier 50, it will cause the second sun wheel 32 andthe second rotor 28 of the second electrical machine 16 to rotate. It isthus possible to allow the second electrical machine 16 to operate as agenerator to supply power to the energy storage device 46, and/or tosupply power to the first electrical machine 14. Alternatively, thesecond electrical machine 16 may also emit a torque injection by way ofthe control device 48, controlling the second electrical machine 16 inorder to provide a propulsion torque.

In order to shift from the fourth gear to the fifth gear, the firstelectrical machine 14 is controlled, in such a way that torque balanceprevails between the first ring gear 22 and the gearbox house 42. Whentorque balance prevails between the first ring gear 22 and the gearhouse 42, the third coupling device 59 is controlled in such a way thatthe first ring gear 22 is disconnected from the gear house 42.Subsequently, the first electrical machine 14 is controlled in such away that a substantially zero torque state arises between thecountershaft 18 and the first cogwheel 64. When a substantially zerotorque state arises between the countershaft 18 and the first cogwheel64, the first coupling element 84 is controlled in such a way that thefirst cogwheel 64 is disconnected from the countershaft 18. Thus, thefourth gear has been disengaged. In order to engage the fifth gear, thefirst electrical machine 14 is controlled in such a way that asynchronous rotational speed arises between the first main shaft 34 andthe output shaft 20. When a synchronous rotational speed arises betweenthe first main shaft 34 and the output shaft 20, the coupling mechanism96 is controlled in such a way that the first main shaft 34 and theoutput shaft 20 are connected and joined with each other. Subsequently,the first electrical machine 14 is controlled in such a way that asubstantially zero torque state arises between the countershaft 18 andthe first cogwheel 92 of the fifth gear pair 21. When a substantiallyzero torque state arises between the countershaft 18 and the fifthcogwheel 92, the fifth coupling element 93 is controlled in such a waythat the fifth cogwheel 92 is disconnected from the countershaft 18.Subsequently, the first electrical machine 14 is controlled in such away that a synchronous rotational speed arises between the countershaft18 and the first cogwheel 64. When a synchronous rotational speed arisesbetween the countershaft 18 and the first cogwheel 64, the couplingelement 84 is controlled in such a way that the first cogwheel 64 isconnected and joined with the countershaft 18. Finally, the combustionengine 4 is controlled in such a way that the second ring gear 28 comesto a standstill in relation to the gear house 42. When the second ringgear 28 is at a standstill, the fourth coupling device 61 is controlledin such a way that the second ring gear 28 is connected and locked withthe gear house 42. Thus, the vehicle 1 is now driven in the fifth gear.

When the fifth gear is engaged, torque from the combustion engine 4 willpass the first and second planetary wheel carriers 50, 51 and betransferred from the second main shaft 36 via the second gear pair 66 tothe countershaft 18, and further along via the first gear pair 60 to thefirst main shaft 34, in order subsequently to be transferred to theoutput shaft 20 via the coupling mechanism 96.

In order to shift from the fifth gear to the sixth gear, the secondelectrical machine 16 is controlled in such a way that torque balanceprevails between the second ring gear 28 and the gear house 42. Whentorque balance prevails between the second ring gear 28 and the gearhouse 42, the fourth coupling device 61 is controlled in such a way thatthe second ring gear 28 is disconnected from the gear house 42.Subsequently the combustion engine 4 is controlled in such a way that asynchronous rotational speed arises between the first sun wheel 26 andthe first planetary wheel carrier 50. When a synchronous rotationalspeed arises between the first sun wheel 26 and the first planetarywheel carrier 50, the first coupling device 56 is controlled in such away that the first sun wheel 26 is connected and joined with the firstplanetary wheel carrier 50. Subsequently, the first electrical machine16 is controlled in such a way that a substantially zero torque statearises between the countershaft 18 and the first cogwheel 64. When asubstantially zero torque state arises between the countershaft 18 andthe first cogwheel 64, the coupling element 84 is controlled in such away that the first cogwheel 64 is disconnected from the countershaft 18.Finally, the second electrical machine 16 is controlled in such a waythat a synchronous rotational speed arises between the countershaft 18and the third cogwheel 76. When a synchronous rotational speed arisesbetween the countershaft 18 and the third cogwheel 76, the couplingelement 88 is controlled in such a way that the third cogwheel 76 isconnected and joined with the countershaft 18. Thus, the vehicle 1 isnow driven in the sixth gear.

When the sixth gear is engaged, torque from the combustion engine 4 willbe transferred from the first planetary wheel carrier 50 to the firstsun wheel 26, and further along to the first main shaft 34, in ordersubsequently to be transferred to the output shaft 20 via the couplingmechanism 96.

In order to shift from the sixth gear to the seventh gear the firstand/or the second electrical machines 14, 16 is controlled in such a waythat torque balance prevails in the second planetary gear 12. Whentorque balance prevails in the second planetary gear 12, the firstcoupling device 56 is controlled in such a way that the first sun wheel26 is disconnected from the first planetary wheel carrier 50.Subsequently the combustion engine 4 is controlled in such a way that asynchronous rotational speed arises between the second sun wheel 32 andthe second planetary wheel carrier 51. When a synchronous rotationalspeed arises between the second sun wheel 32 and the second planetarywheel carrier 51, the second coupling device 58 is controlled in such away that the second sun wheel 32 is connected and joined with the secondplanetary wheel carrier 51. Thus, the vehicle 1 is now driven in theseventh gear.

When the seventh gear is engaged, torque from the combustion engine 4will pass the first planetary wheel carrier 50 and further along to thesecond main shaft 36. Subsequently, torque is transferred from thesecond main shaft 36 via the second gear pair 66 to the countershaft 18,and further via the third gear pair 72 to the first main shaft 34, inorder subsequently to be transferred to the output shaft 20 via thecoupling mechanism 96.

According to the embodiment above, the gearbox 2 comprises pinion gears62, 68, 74, 80 and cogwheels 64, 70, 76, 82 arranged on the main shafts34, 36 and the countershaft 18, respectively, to transfer rotationalspeed and torque. However, it is possible to use another type oftransmission, such as chain and belt drives, to transfer rotationalspeed and torque in the gearbox 2.

The transmission device 19 has four gear pairs 60, 66, 72, 78 accordingto the example embodiment. However, the transmission device 19 maycomprise any number of gear pairs.

FIG. 3 illustrates the hybrid powertrain 3 according to FIG. 2 is asimplified schematic view, where some components have been excluded inthe interest of clarity. FIG. 3 shows a gear pair G1, connected with thefirst main shaft 34 and therefore with the first planetary gear 10, anda gear pair G2, connected with the second main shaft 36 and thereforewith the second planetary gear 12. These gear pairs G1, G2 are alsoconnected to the output shaft 20 via the countershaft 18. The gear pairG1, connected with the first main shaft 34, may for example consist ofthe first gear pair 60 or the third gear pair 72, as described in FIG. 2and may comprise additional gear pairs. The gear pair G2, connected withthe second main shaft 36, may for example consist of the second gearpair 66 or the fourth gear pair 78, as described in FIG. 2 and maycomprise additional gear pairs. Further, the fifth gear pair G3, 21,connected with the output shaft 20 and the countershaft 18 is displayed,which is also described in FIG. 2. However, G3 may consist of additionalgear pairs. Alternatively, torque may be extracted directly from thecountershaft 18, which thus constitutes the output shaft.

The at least one gear pair G1, 60, 72, connected with the firstplanetary gear 10 comprises at least one pinion gear 62, 74 and onecogwheel 64, 76 arranged in engagement with each other, which piniongear 62, 74 may be arranged in such a way that it may be connected withand disconnected from the main shaft 34, arranged with the firstplanetary gear 10. The at least one cogwheel 64, 76 may be arranged sothat it may be connected with and disconnected from the countershaft 18.

The at least one gear pair G2, 66, 78, connected with the secondplanetary gear 12, comprises at least one pinion gear 68, 80 and onecogwheel 70, 82 arranged in engagement with each other, which piniongear 68, 80 may be arranged in such a way that it may be connected withand disconnected from the second main shaft 36, arranged with the firstplanetary gear 12. The at least one cogwheel 70, 82 may be arranged sothat it may be connected with and disconnected from the countershaft 18.

As described, torque is extracted from the gearbox 2 from the outputshaft 20. It is also possible to extract torque directly from the firstor second main shaft 34, 36, or directly from the countershaft 18, whichin this case constitutes the output shaft 20. Torque may also beextracted in parallel from two or all of the three shafts 18, 34, 36simultaneously.

According to FIG. 3 the third and fourth coupling devices 59 and 61 havebeen excluded. According to this embodiment of the invention, it isstill possible to drive the vehicle in a number of operating modes anddriving modes. As an example, the shift from one gear to another will bedescribed. The components displayed in FIG. 2 and FIG. 3 is used todescribe the shifting process. A gear is engaged when the first couplingdevice 56 is connected, and thus joins the first sun wheel 26 and afirst planetary wheel carrier 50 arranged in the first planetary gear 10with each other, while simultaneously the second coupling device 58 isdisconnected, and thus disconnects the second sun wheel 32 and thesecond planetary wheel carrier 51, arranged in the second planetary gear12, are from each other. At this gear the first main shaft 34 isoperated by the output shaft 97 of the combustion engine 4 and, whenneeded, by the first electrical machine 10, which results in the firstmain shaft 34 operating the first pinion gear 62. Since the firstcogwheel 64 is in engagement with the first pinion gear 62 and isconnected with the countershaft 18 via the first coupling element 84,the first cogwheel 64 will operate the countershaft 18, which in turnoperates the fifth cogwheel 92 on the countershaft 18. The fifthcogwheel 92 in turn operates the output shaft 20 of the gearbox 2 viathe sixth cogwheel 94, which is arranged on the output shaft 20 of thegearbox 2.

In order to shift to a next gear, the second electrical machine 16 iscontrolled in such a way that a propulsion torque is generated via thesecond main shaft 36 and via the second gear pair 66, whereat the secondcogwheel 70 of the second gear pair 66 is connected to the countershaft18 via the second coupling element 86. The propulsion torque furthertransmitted via the fifth gear pair 21 and finally to the output shaft20.

In order to disengage the first cogwheel 64 from the countershaft 18, sothat the fourth gear is disconnected, the combustion engine 4 and thefirst electric machine 14 are first controlled in such a way that thefirst cogwheel 64 is brought to a substantially zero torque state inrelation to the countershaft 18. When a substantially zero torque statehas arisen, the first coupling element 84 is disengaged, so that thefirst cogwheel 64 is disconnected from the countershaft 18.

Subsequently, the rotational speed of the first main shaft 34 issynchronized with the rotational speed of the output shaft 20, followingwhich the coupling mechanism 96 is controlled in such a way that itconnects the first main shaft 34 with the output shaft 20.

Subsequently, the combustion engine 4 and the first electrical machine14 are controlled in such a way that the propulsion torque occurs viathe first main shaft 34 and via the coupling mechanism 96, and furtheralong to the output shaft 20. By reducing the torque from the secondelectrical machine 16, the fifth coupling element 93 may be brought to asubstantially zero torque state in relation to the countershaft 18. Whena substantially zero torque state has arisen, the fifth coupling element93 is disengaged, so that the fifth cogwheel 92 of the fifth gear pair21 is disconnected from the countershaft 18.

Subsequently, with the help of the second electrical machine 16, therotational speed of the countershaft 18 is synchronized with the enginespeed of the third cogwheel 76, following which the third couplingelement 88 is controlled in such a way that it connects the thirdcogwheel 76 with the countershaft 18. When this connection has beencompleted, the propulsion torque may be shared between the combustionengine 4, the first electrical machine 14 and the second electricalmachine 16. Subsequently, torque balance is created in the firstplanetary gear 10, following which the first coupling device 56disconnects the first planetary wheel carrier 50 and the first sun wheel26 from each other. Finally, the second planetary wheel carrier 51 isrotational speed synchronized with the second sun wheel 32, followingwhich the second coupling device 58 connects the second planetary wheelcarrier 51 and the second sun wheel 32 with each other.

As described, torque is extracted from the gearbox 2, from the outputshaft 20. It is also possible to extract torque directly from the firstor second main shaft 34, 36, or directly from the countershaft 18.Torque may also be extracted in parallel from two or all of the threeshafts 18, 34, 36 simultaneously.

Below, embodiments to start the combustion engine 4 are described. Thethird and fourth coupling devices 59 and 61 have been excluded, sincethey are not needed in the method to start the combustion engine 4.

In order to start the combustion engine 4, the second sun wheel 32 ofthe second planetary gear 12 and the second planetary wheel carrier 51are also connected with each other, with the use of the second couplingdevice 58.

According to a first embodiment, the first cogwheel 64 of the first gearpair 60 is connected to the countershaft 18, so that the first cogwheel64 is prevented from rotating in relation to the countershaft 18, andthe output shaft 20 is prevented from rotating with the fifth gear pair21, arranged between the countershaft 18 and the output shaft, since thefifth cogwheel 92 is locked on the countershaft 18. The second cogwheel70 is disconnected from the countershaft, so that the second gear pair66 may rotate freely. The coupling mechanism 96 is closed. Thecombustion engine 4 is started by activating the first electricalmachine 14 and the second electrical machine 16, by supplying energy tothe first and the second electrical machines 14, 16, so that the firstand second electrical machines 14, 16 rotate in the direction of theoutput shaft 97 of the combustion engine 4, when the combustion engine 4is activated.

According to a second embodiment, the first and the fifth cogwheels 64,92 are disconnected from the countershaft 18, so that the first and thefifth gear pairs 60, 21 are free to rotate and the coupling mechanism 96is opened. The second gear pair 66 rotates freely. The output shaft 20is prevented from rotating with a brake device 7 for the driving wheels6 of the vehicle 1, so that the vehicle 1 comes to a standstill. Thecombustion engine 4 is started by activating the first electricalmachine 14 and the second electrical machine 16, by supplying energy tothe first and the second electrical machines 14, 16, so that the firstand second electrical machines 14, 16 rotate in the direction of theoutput shaft 97 of the combustion engine 4, when the combustion engine 4is activated.

According to a third embodiment, the first sun wheel 26 of the firstplanetary gear 10 and the first planetary wheel carrier 50 are connectedwith each other, with the help of the first coupling device 56, whilethe second sun wheel 32 of the second planetary gear 12 and the secondplanetary wheel carrier 51 are connected with each other via the secondcoupling device 58. The first, second and fifth gear pairs 60, 66, 21rotate freely, the coupling mechanism 96 is open and the brake device 7for the driving wheels 6 of the vehicle 1 is released. The combustionengine 4 is started by activating the first electrical machine 14 andthe second electrical machine 16, by supplying energy to the first andthe second electrical machines 14, 16, so that the first and secondelectrical machines 14, 16 rotate in the direction of the output shaft97 of the combustion engine 4, when the combustion engine 4 isactivated.

As described, torque is extracted from the gearbox 2, from the outputshaft 20. It is also possible to extract torque directly from the firstor second main shaft 34, 36, or directly from the countershaft 18.Torque may also be extracted in parallel from two or all of the threeshafts 18, 34, 36 simultaneously.

FIG. 4 shows a flow chart relating to a first method to start thecombustion engine 4 in a hybrid powertrain 3 to achieve shifting withoutany torque interruption, comprising a gearbox 2 with an input shaft 8and an output shaft 20; which combustion engine is connected to theinput shaft 8; a first planetary gear 10, which is connected to theinput shaft 8: a second planetary gear 12, connected to the firstplanetary gear 10; a first electrical machine 14, connected to the firstplanetary gear 10; a second electrical machine 16, connected to thesecond planetary gear 12; at least one gear pair G1, 60, 72 connectedwith the first planetary gear 10 and the output shaft 20; and at leastone gear pair G2, 66, 78 connected with the second planetary gear 12 andthe output shaft 20.

The method comprises the steps:

a) connecting the rotatable components 32, 51 of the second planetarygear 12 with each other, by connecting, with a second coupling device58, a second sun wheel 32 arranged in the second planetary gear 12 and asecond planetary wheel carrier 51 with each other, and

b) activating the first electrical machine 14 and the second electricalmachine 16, so that the combustion engine 4 starts.

Preferably the combustion engine 4 is connected with a first planetarywheel carrier 50, arranged in the first planetary gear 10, which isconnected with a second sun wheel 32 arranged in the second planetarygear 12.

In step a) a second sun wheel 32 arranged in the second planetary gear12, and a second planetary wheel carrier 51, are connected with the helpof a second coupling device 58.

After step a) and before step b) the output shaft 20 is prevented fromrotating in step c).

Preferably, the at least one gear pair G1, 60, 72, which is connectedwith the first planetary gear 10 and the output shaft 20, comprises apinion gear 62 and a first cogwheel 64 in engagement with each other,which first pinion gear 62 is fixedly arranged with the first planetarygear 10 and which first cogwheel 64 is arranged so that it may beconnected with and disconnected from a countershaft 18, wherein afterstep a) and before step b), in step c) the first cogwheel 64 isconnected to the countershaft, so that the first cogwheel 64 isprevented from rotating in relation to the countershaft 18, and theoutput shaft 20 is prevented from rotating with the use of at least onegear pair G3, 21, which is connected with a countershaft 18 and theoutput shaft 20.

Preferably, the at least one gear pair G3, 21, which is connected with acountershaft 18 and the output shaft 20, comprises a fifth and a sixthcogwheel 92; 94 in engagement with each other, which fifth cogwheel 92is arranged so that it may be connected with and disconnected from thecountershaft 18 with the use of a fifth coupling element 93, and thefifth cogwheel 92 is locked to the countershaft 18 in step c).

Preferably, a coupling mechanism 96 is arranged between the firstplanetary gear 10 and the output shaft 20, and in step c) the couplingmechanism 96 is locked, so that the first planetary gear 10 is connectedwith the output shaft 20.

The second embodiment of the method is displayed in the flow chart inFIG. 5. After step a) and before step b), in step d) the output shaft 20is preferably prevented from rotating with a brake device 7 for thedriving wheels 6 of a vehicle 1, to which driving wheels 6 the outputshaft 20 is connected.

The third embodiment of the method is displayed in the flow chart inFIG. 6. Before step a), in step e) preferably the rotatable components26, 50 of the first planetary gear 10 are connected with each other.

In step e) preferably a first sun wheel 26 arranged in the firstplanetary gear 10, and a first planetary wheel carrier 50, are connectedwith the use of a first coupling device 56.

After step a) and before step b), in step f) the first and the secondgear pairs 60, 66 are released, so that they are free to rotate.

The at least one gear pair G1, 60, 72, which is connected with the firstplanetary gear 10 and the output shaft 20, comprises a pinion gear 62and a first cogwheel 64 engaged with each other, which first pinion gear62 is fixedly arranged with the first planetary gear 10, and which firstcogwheel 64 is arranged so that it may be connected with anddisconnected from a countershaft 18; and also comprises a third piniongear 74 and a third cogwheel 76 engaged with each other, which thirdpinion gear 74 is fixedly arranged with the first planetary gear 10, andwhich third cogwheel 76 is arranged so that it may be connected with anddisconnected from the countershaft 18, wherein in step f) the first andthe second cogwheels 64, 70 are disconnected from the countershaft, sothat the first and the second gear pairs 60, 66 are free to rotate.

The at least one gear pair G2, 66, 78, which is connected with thesecond planetary gear 12 and the output shaft 20, comprises a secondpinion gear 68 and a second cogwheel 70 engaged with each other, whichsecond pinion gear 68 is fixedly arranged with the second planetary gear12, and which second cogwheel 70 is arranged so that it may be connectedwith and disconnected from a countershaft 18; and also comprises afourth pinion gear 80 and a fourth cogwheel 82 engaged with each other,which fourth pinion gear 80 is fixedly arranged with the secondplanetary gear 12, and which fourth cogwheel 82 is arranged so that itmay be connected with and disconnected from the countershaft 18, whereinin step f) the first and the second cogwheels 64, 70 are disconnectedfrom the countershaft, so that the first and the second gear pairs 60,66 are free to rotate.

According to the invention, a computer program P is provided, stored inthe control device 48 and/or the computer 53, which computer program maycomprise procedures to start the combustion engine 4 according to thepresent invention.

The program P may be stored in an executable manner, or in a compressedmanner, in a memory M and/or a read/write memory R.

The invention also relates to a computer program product, comprisingprogram code stored in a medium readable by a computer, in order toperform the method steps specified above, when said program code isexecuted in the control device 48, or in another computer 53 connectedto the control device 48. Said program code may be stored in anon-volatile manner on said medium readable by a computer 53.

The components and features specified above may, within the framework ofthe invention, be combined between different embodiments specified.

1. A method to start a combustion engine in a hybrid powertrain,comprising a gearbox with an input shaft and an output shaft; whichcombustion engine is connected to the input shaft; a first planetarygear, which is connected to the input shaft: a second planetary gear,connected to the first planetary gear; a first electrical machine,connected to the first planetary gear; a second electrical machine,connected to the second planetary gear; at least one gear pair,connected with the first planetary gear and the output shaft; and atleast one gear pair, connected with the second planetary gear and theoutput shaft, said method comprising: a) connecting the rotatablecomponents of the second planetary gear with each other, by connecting,with a second coupling device, a sun wheel arranged in the secondplanetary gear and a second planetary wheel carrier with each other; andb) activating the first electrical machine and the second electricalmachine, so that the combustion engine starts.
 2. A method according toclaim 1, wherein the combustion engine is connected with a firstplanetary wheel carrier arranged in the first planetary gear, which isconnected with a second sun wheel, arranged in the second planetarygear.
 3. A method according to claim 1, wherein that after step a) andbefore step b), in step c), the output shaft is prevented from rotating.4. A method according to claim 3, wherein the at least one gear pair,which is connected with the first planetary gear and the output shaft,comprises a first pinion gear and a first cogwheel engaged with eachother, which first pinion gear is arranged with the first planetarygear, and which first cogwheel is arranged on a countershaft, wherein instep c) the first pinion gear and the first cogwheel are connected withthe first planetary gear and the countershaft, respectively, and in thatthe output shaft is connected with the countershaft via a gear pair,connected with the countershaft and the output shaft.
 5. A methodaccording to claim 4, wherein that the at least one gear pair, which isconnected with a countershaft and the output shaft comprises a fifth andsixth cogwheel in engagement with each other, which fifth cogwheel isarranged so that it may be connected with and disconnected from thecountershaft with the use of a fifth coupling element, and in that thefifth cogwheel is locked to the countershaft in step c).
 6. A methodaccording to claim 3, wherein a coupling mechanism is arranged betweenthe first planetary gear and the output shaft, and in that in step c)the coupling mechanism is locked, so that the first planetary gear isconnected with the output shaft.
 7. A method according to claim 3,wherein in step c) the output shaft is prevented from rotating with abrake device for the driving wheels of a vehicle, to which drivingwheels the output shaft is connected.
 8. A method according to claim 1,wherein before step a), instep e), the first planetary gear's rotatablecomponents are connected with each other in step e),
 9. A methodaccording to claim 8, wherein in step e), a first sun wheel arranged inthe first planetary gear and a first planetary wheel carrier areconnected with each other, with the use of a first coupling device. 10.A method according to claim 8, wherein after step a) and before step b),in step f) the first and second gear pairs are released, so that theymay freely rotate.
 11. A method according to claim 10, wherein the atleast one gear pair, which is connected with the first planetary gearand the output shaft comprises a first pinion gear and a first cogwheelin engagement with each other, which first pinion gear is fixedlyconnected with the first planetary gear, and which first cogwheel isarranged so that it may be connected with or disconnected from acountershaft ; and also comprises a third pinion gear and a thirdcogwheel engaged with each other, which third pinion gear is fixedlyarranged with the first planetary gear, and which third cogwheel isarranged so that it may be connected with or disconnected from thecountershaft, wherein in step f) the first and second cogwheels aredisconnected from the countershaft, so that the first and second gearpairs may freely rotate.
 12. A method according to claim 10, wherein theat least one gear pair, which is connected with the second planetarygear and the output shaft, comprises a second pinion gear and a secondcogwheel in engagement with each other, which second pinion gear isfixedly connected with the second planetary gear, and which secondcogwheel is arranged so that it may be connected with or disconnectedfrom a countershaft; and also comprises a fourth pinion gear and afourth cogwheel engaged with each other, which fourth pinion gear isfixedly arranged with the second planetary gear, and which fourthcogwheel is arranged so that it may be connected with or disconnectedfrom the countershaft, wherein in step f) the first and second cogwheelsare disconnected from the countershaft, so that the first and secondgear pairs may rotate freely.
 13. A vehicle with a hybrid powertrain,said hybrid powertrain comprising: a gearbox with an input shaft and anoutput shaft; which combustion engine is connected to the input shaft; afirst planetary gear, which is connected to the input shaft; a secondplanetary gear, connected to the first planetary gear; a firstelectrical machine, connected to the first planetary gear; a secondelectrical machine, connected to the second planetary gear; at least onegear pair, connected with the first planetary gear and the output shaft;and at least one gear pair, connected with the second planetary gear andthe output shaft; and an electronic control device, set up to controlthe hybrid drive line to start the combustion engine, said electroniccontrol device configured to: a) connect the rotatable components of thesecond planetary gear with each other, by connecting, with a secondcoupling device, a sun wheel arranged in the second planetary near and asecond planetary wheel carrier with each other; and b) activate thefirst electrical machine and the second electrical machine, so that thecombustion engine starts.
 14. (canceled)
 15. A computer program productcomprising computer program code stored on a non-transitory computerreadable medium readable by a computer to start a combustion engine in ahybrid powertrain, comprising a gearbox with an input shaft and anoutput shaft; which combustion engine is connected to the input shaft; afirst planetary gear, which is connected to the input shaft: a secondplanetary gear, connected to the first planetary gear; a firstelectrical machine, connected to the first planetary gear; a secondelectrical machine, connected to the second planetary gear; at least onegear pair, connected with the first planetary gear and the output shaft;and at least one gear pair, connected with the second planetary gear andthe output shaft, said computer program code comprising computerinstructions to cause one or more computer processors to perform theoperations of: a) connecting the rotatable components of the secondplanetary gear with each other, by connecting, with a second couplingdevice, a sun wheel arranged in the second planetary gear and a secondplanetary wheel carrier with each other; and b) activating the firstelectrical machine and the second electrical machine, so that thecombustion engine starts.